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Review of / Measurement on ML-102 Charger

This charger is a very small 18650 charger, it need an external USB power source to charge, and can also work as a USB charger. It only charges one battery at a time.

Only a USB cable is included with the charger, I did also order some spacers, making it possible to charge smaller batteries.

The charger is powered from any USB source that can supply 1A, sadly it uses the mini and not the micro USB connector (The micro USB is much stronger and is the common charge connector on phones). Because the connector is on the side of the charger it is not possible to place a couple of these chargers beside each other.

The charger also has a full size USB connection for power out, it can be used to charge a phone or other USB equipment.

The charger has a couple of leds, one is placed on top of the charger and some other inside the charger.
The light is red when charging, both red and green when nearly full, green when finished and blue when supplying USB power.

The plus connection is slightly raises, making it possible to charger flat top batteries, the spring at the minus connection is rather short, but long enough to support unprotected 18650 batteries.

With the two spacers (Each 15.9 mm long) I included in my order the charger can also handle xx500 and xx340 cell, but the charger current is too high for many of these batteries.

The charger can handle 69.6 mm long batteries, including flat top cells. Not all 26650 can be charged, it depends on the size and shape of the plus pole on the battery. With the spacers it is also possible to use smaller batteries, but watch the maximum charge current for the battery type!

Measurements

Below 2.8 volt the charger charges with 130 to 170 mA (Highest current at lowest voltage).
Between 2.8 volt and 4.2 volt the charger is applying regular charge current (See curve below).
When the charge current goes below 70mA the charging is stopped and it will discharge with less than 75 uA.
The charger will restart when the battery drops to 4.12 volt or power is cycled.
Reinserting the battery will not restart charging.
When charger is disconnected from power, but with a battery in, it will draw below 75uA from the battery.

The charge curve does not look like a CC/CV charger, but the only disadvantage with this type of curve is the slower charge speed, the final result will be just as good as a CC/CV charger. The termination current is around 80mA, this is a good value.
The above curve is done with a USB power supply (or more correctly a lab power supply adjusted to 5 volt).

Using a laptop as power supply does not change the charge curve significantly. The charger is using nearly 1A from the USB connector, this is more than allowed in the USB specifications, but nearly always works fine.

What happens if a weak USB power supply is used or long cables, to simulate that I turned the power supply down to 4.5 volt. The charger continues to charge and stops when the battery is full, but it takes considerable longer time (nearly 10 hours).

The charger also handles my old IMR cell without any problems.

Measurements on USB power

The charger can supply USB power while discharging the battery. It is possible to connect a USB power supply to the charger and connect the charger to some USB equipment and charge both at the same time.

USB specification says the voltage must be between 4.75 and 5.25 volt, I have placed a yellow line at 4.75 volt in the charts.

The first curve is with a 20 ohm load, this gives a load current of 250 mA, the usb output stays exactly at 5.13 volt, until the battery is empty. It keeps a very good efficiency at about 90%.
The power is turned off when the battery is down to 3 volt and it does not turn on again when the battery voltage increases, this is a good design.

Reducing the resistor increases the current to 500 mA and drops the voltage to 5.1 volt (probably due to cable losses). The efficiency is still very good at 85% to 90%.

Reducing the resistor again increases the current to 550 mA, the efficiency is starting to drop now, but the voltage is stable.

This time I have increased the current to 650 mA and this is at the limit of the circuit, the voltage is not stable anymore, but it can still supply this current for two hours and stay within the USB specifications.

Conclusion

This charger is a very compact LiIon charger with dual functionality (Can both charger USB devices and 18650 batteries), the charging profile is good, but not optimal for speed. I can see two obvious applications for this charger, one is for people with only a few 18650 batteries, the other is in a travel kit, where the ability to charger USB equipment from an 18650 battery can be very useful.
I like this charger and is going to add it to my traveling kit.

Re: Review of / Measurement on ML-102 Charger

I recently purchased a couple of these chargers and I have one concern. I was charging a battery and it seemed to be on red/green for longer than normal so I took it off. It was 4.22V. I put it back on the charger and it was still red/green. So I put it in my other ML-102 charger and it stayed green as you would expect. Finally I unplugged then plugged back in the original charger I used and it stayed green! Very strange.

Re: Review of / Measurement on ML-102 Charger

Originally Posted by rufus001

I recently purchased a couple of these chargers and I have one concern. I was charging a battery and it seemed to be on red/green for longer than normal so I took it off. It was 4.22V. I put it back on the charger and it was still red/green. So I put it in my other ML-102 charger and it stayed green as you would expect. Finally I unplugged then plugged back in the original charger I used and it stayed green! Very strange.

Could it be the protection circuit of your battery which didn't kick in so it kept on charging? Maybe after taking it out then putting it back, that was when it realized it was already up to 4.22V. But I read somewhere that the cut off for these cells are in the 4.25volt range.

Re: Review of / Measurement on ML-102 Charger

Originally Posted by roadkill1109

Could it be the protection circuit of your battery which didn't kick in so it kept on charging? Maybe after taking it out then putting it back, that was when it realized it was already up to 4.22V. But I read somewhere that the cut off for these cells are in the 4.25volt range.

It could be. One of the other batteries I ordered from the same place was DOA.

Re: Review of / Measurement on ML-102 Charger

Originally Posted by rufus001

It could be. One of the other batteries I ordered from the same place was DOA.

Ouch! At least the charger's working.

It's cool that with one Panasonic 3100mAh, i am able to fully charge my Blackberry Bold 9900, and charge my Nokia 5800XM to 75% before the battery croaks! Dropped down to a safe 3volt just right for re-charging.

Re: Review of / Measurement on ML-102 Charger

A very good review, HKJ, congratulations.

I have two ML-102 and I am very satisfied with the purchase, both function well so much upon charging the battery as upon delivering energy by the USB port. I expect that arrive quickly the Blue Led Panel Meter to be able to weld them to him the charger. My intention is to use them in my next trip to the desert in bicycle to maintain charged the batteries of the flashlights.

Re: Review of / Measurement on ML-102 Charger

Originally Posted by rufus001

I recently purchased a couple of these chargers and I have one concern. I was charging a battery and it seemed to be on red/green for longer than normal so I took it off. It was 4.22V. I put it back on the charger and it was still red/green. So I put it in my other ML-102 charger and it stayed green as you would expect. Finally I unplugged then plugged back in the original charger I used and it stayed green! Very strange.

I've got two of the chargers and have found exactly the same results! One always charges to 4.22V while the other charges to 4.20V. I can't work it out, but then again, I'm a bit of an ape when it comes to these things. I wonder if the discharge cut-off is 0.02V different too...

Re: Review of / Measurement on ML-102 Charger

Originally Posted by gravelmonkey

I've got two of the chargers and have found exactly the same results! One always charges to 4.22V while the other charges to 4.20V. I can't work it out, but then again, I'm a bit of an ape when it comes to these things. I wonder if the discharge cut-off is 0.02V different too...

Re: Review of / Measurement on ML-102 Charger

Originally Posted by gravelmonkey

I've got two of the chargers and have found exactly the same results! One always charges to 4.22V while the other charges to 4.20V. I can't work it out, but then again, I'm a bit of an ape when it comes to these things.

This kind of difference is expected, there will always be some tolerance on a cheap charger chip.

Re: Review of / Measurement on ML-102 Charger

Originally Posted by HKJ

This kind of difference is expected, there will always be some tolerance on a cheap charger chip.

Thanks HKJ! As a related point, would it be stupid to daisy-chain 2 chargers together? I'm thinking of linking my Cottonpickers solar 1000ma panel to a ML-102 with a salvaged panasonic CGR18650 charging a second ML-102 with an AW 14500 or 18650. Thinking that the panasonic in the first charger would provide a 'buffer' when the sun goes in.

Re: Review of / Measurement on ML-102 Charger

Originally Posted by gravelmonkey

Thanks HKJ! As a related point, would it be stupid to daisy-chain 2 chargers together? I'm thinking of linking my Cottonpickers solar 1000ma panel to a ML-102 with a salvaged panasonic CGR18650 charging a second ML-102 with an AW 14500 or 18650. Thinking that the panasonic in the first charger would provide a 'buffer' when the sun goes in.

That will not really get your anything, except some wasted power (Boosting voltage from a LiIon up to 5 volt looses power).

It can be good idea to have a battery between the solar system and the charger, to get stable power for the charger, this is especially important with NiMH batteries, not as much with LiIon.
But for the first battery, I will recommend a battery/charger that is designed for exactly this purpose, i.e. buffering solar cells.

Re: Review of / Measurement on ML-102 Charger

I tried a couple single 18650 USB chargers and this is by far the best I've tested, if only I've read your review a bit sooner it would have spared me from spending a lot of money lots of frustration with Chinese crap not performing as advertised.

With an Eagletac 3400mAh battery it can charge my iPhone 1,5 times and an EN-EL15 Nikon DSLR battery for 60% with the Pixo Li-Ion/NiMH USB charger.

It charges the iPhone 5 at 0.725A while the phone can handle 0.8A, charging will stop when the charge current goes below 0.2A which happens around 3.3V if memory serves me well. It charges the iPad Mini at a slightly higher current but not close to the 1A it can handle. With the Pixo charger it delivers 0.9A which is the max the charger can handle.

As these chargers are really cheap (fasttech sells them for $7,50) and they are a key item in my mobile hiking/travel powerkit I bought 4 of them just in case they go out of circulation

Re: Review of / Measurement on ML-102 Charger

I just got a ML-102 v3. Works fine, but I have protected Panasonic 3100's which are 69.5 mm long and are a tight fit into the charger. Tight enough that it is denting the bottom of the cells.
Just 4 screws to take it apart. I'll take off a couple of turns off the spring and maybe reduce the height of the positive connector. Should be enough.

Re: Review of / Measurement on ML-102 Charger

Purchased a ML-102 based on this review and thread. Thanks for the great info. I have tried other, cheaper, chargers/battery backups. This is worth the slightly extra $. Well made, compact, reliable! I plan to take it backpacking and use as an emergency source for my phone. Already carry the 18650's for my flashlight and headlight. Great review.

Review of / Measurement on ML-102 Charger

I just used mine on a backpacking trip & the mesh pocket on the back of my pack was filled with snow
while I was sliding down a high mtn pass.
The ML102 was covered in snow for a few hrs until I stopped to camp.

Re: Review of / Measurement on ML-102 Charger

It's really too bad this is apparently at revision 5, but still they haven't switched the mini usb port with micro usb yet. You'd think that would be the first improvement they made. If it needs anything but a micro usb cable, chances are I havenŠt got the cable when I need it.

Are there any alternatives that are almost as small, has micro usb, are fully encased, and approved by HKJ?

ML-102 possible on solar panel ? voltage regulator required ?

hey, i'm planing a long bike trip and i want to charge some 18650 via solar panel. After some research i decided to take the ML-102.
do you think, its possible to charge 18650 in combination with this panel ? would i need a voltage regulator or is the ML 102 capable of the variating voltage out of the solar panel ?
thank you very much
daniel from germany